Steve's Herpetological Blog

An insight into the life of Steve, his research and the many books he reads


#SciFri: Venomous caecilians

You may have seen this article (or one like it) at the beginning of the month, which caused a stir among the amphibian research community. As a group caecilians are severely understudied due to their fossorial nature which makes surveying for them pretty difficult. Whilst it is true that some species are aquatic and live in bodies of water, not all of these worm-like amphibians do. Taking a quick look at the Amphibian Species of the World website (the go-to source for information on amphibian taxonomy), 214 species are currently recognised. All of these are restricted to the tropics and my money is certainly on there being a lot more waiting to be found.

They’re often found whilst digging holes or trenches in the rainforest, although I’ve often wondered how you went about doing this safely without severing them in two. Some species undergo dermatophagy where the young eat the skin of their mother (whilst she is still alive) to provide them with their first meal. As vertebrates go, you can’t get much weirder than a caecilian – which makes them super cool in their own right. The news that they may be venomous elevates this even further. If the fact that they looked like something out of a Ridley Scott film and are extremely elusive wasn’t enough, this certainly puts the icing on the cake.

The biggest revelation from this news is that another group of amphibians have found to have venom, although the delivery mechanism differs from the two known venomous frogs (you can read more about them here). It makes sense that caecilians would have venomous saliva as this is where and how we think snakes evolved venom (based on the current science). To me the most profound question we have to ask from all of this is were caecilians the first limbless vertebrates to posses venom with snakes copying and perfecting this design, or not? Of course there is still lots we do not know about this venomous saliva but as usual with caecilians, they always lead to more questions being asked than answered.

I’m looking forward to following this research to see where it goes. Unfortunately I’ve never seen a caecilian in the wild (despite looking) but there is always next time I guess! What are your thoughts on venomous caecilians?

Cover photograph by Joel Sartore (National Geographic Photo Ark).

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